Cancer and Obesity

Excessive Weight is Linked to Cancer

Years ago I read a book entitled, Heart Disease, about the relationship between heart disease and diets. I still remember how that book jolted me into changing the way I look at my weight, daily diet and exercise.

You may be surprised to learn that excessive weight is also associated with cancer. This is true for men as well as women.

The Winter 1999 Newsletter of the American Institute for Cancer Research on Diet, Nutrition and Cancer Prevention featured an article entitled, “The Obesity Factor: Excessive Weight Has Strong Cancer Links.”

“If there were ever any doubts about the effects of obesity on your health,” the author writes, “two major international reports put them to rest.” The two reports –

  1. Food, Nutrition and the Prevention of Cancer: a Global Perspective by AICR found “evidence that obesity increases the risk of cancers of the uterus, breast and kidney and possibly of the colon and gall bladder.”
  2. Obesity: Preventing and Managing the Global Epidemic by the World Health Organization, for the first time “identifies obesity as a disease” and goes on to highlight the chronic problems caused by excessive weight – including diabetes, hypertension, heart disease and cancer.

I wanted to know more about the links between cancer and obesity, so I visited the websites. Food, Nutrition and the Prevention of Cancer was sponsored by the World Cancer Research Fund and the AICR. It took five years to complete and was first published in 2007. It is thought to be the most definitive report of its kind.

It is based on findings and recommendations of an expert panel based on assessment of voluminous scientific studies by an expert task force and review of extensive literature by research teams.

Although the main focus of the report is on nutritional and other factors the modify the risk of cancer, one chapter in the report spotlighted obesity which the report says, “is or may be a cause of a number of cancers.”

In 2009 AICR estimated that over 100,000 cancers occur every year in the U.S. due to excess body fat. They based their estimate on the findings of the monumental report and the latest U.S. cancer data.

New cases of cancer by type included –

49% of endometrial cancers 20,700 cases/year
35% of esophageal cancers 5,800 cases/year
28% of pancreatic cancers -11,900 cases/year
24% of kidney cancers -13,900 cases/year
21% of gallbladder cancers 2,000 cases/year
17% of breast cancers -33,000 cases/year
9% of esophageal cancers -13,200 cases/year

“We now know that carrying excess body fat plays a central role in many of the most common cancers,” according to Laurence Kolonel, MD, PhD, Deputy Director of the Cancer Research Center of Hawaii and AICR/WCRF expert panel member when he presented the estimates. “And it’s clearer than ever that obesity’s impact is felt before, during and after cancer – it increases risk, makes treatment more difficult and shortens survival.”

The connection between obesity and cancer

Dr. Kolonel explained the emerging evidence of the connection. Excess body fat increases the body’s level of sex steroids and other hormones that are linked to cancer growth. For example, fat tissue produces estrogen which promotes cell proliferation in breast tumors that contain receptors for the hormone, the so-called ER positive tumors. Excess body fat also lowers immune function and increases oxidative stress, which can lead to DNA damage.

The Fall 1999 AICR Newsletter article asks, “How does Body Fat Increase Cancer Risk?” The article highlights connections between fat tissue and hormones, steroids, the immune system, and more.

According to Dr. Ferro-Luzzi, member of ACIR’s expert panel, “There is more estrogen in the blood of an obese woman.” Why is that so? One possible answer is that “fat converts the male hormone androgen “(which women have as well as men) “into the female hormone estrogen” increasing estrogen levels and possibly leading to cancers of the uterus and breast in women.

“How obesity affects kidney and colon cancers is less clear,” the article says. “Hormonal factors and the way the body metabolizes fat may be behind an increased kidney cancer risk.” As for colon cancer a partial explanation is the amount of time substances take through the large intestine. The longer the travel time, the higher the risk. “Physical activity might reduce transit time and shorten the time the lining of the colon is exposed to cancer –causing substances,” according to Ferro-Luzzi. “Obese individuals may be less physically active, which can slow transit time and increase cancer risk.”

Another link to cancer cited by Ferro-Lucci is that “obesity promotes a general environment of growth in the body” and that “cells, including cancer cells, grow more easily when fuel is plentiful.”

The Mayo Clinic and others suggest that obesity may also be a risk factor for breast cancer in men, because it increases the number of fat cells in the body. Fat cells convert androgens into estrogen, which may increase the amount of estrogen in the body and, therefore, the risk of breast cancer.

The growing evidence of the connection between excessive weight and cancer is convincing! Now, what can you do about it?

Lower your risk of getting cancer through diet and exercise

Fitness and weight recommendations from the report, Food, Nutrition and the Prevention of Cancer:

  • Be as lean as possible within the normal range of body weight.
  • Maintain body weight within the normal range from age 21.
  • Avoid weight gain and increases in waist circumference throughout adulthood.
  • Be physically active as part of everyday life.
  • Be moderately physically active, equivalent to brisk walking, for at least 30 minutes every day
  • As fitness improves, aim for 60 minutes or more of moderate, or for 30 minutes or more of vigorous, physical activity every day.
  • Limit sedentary habits such as watching television.

Diet recommendations from the report, Food, Nutrition and the Prevention of Cancer:

  • Consume energy-dense foods sparingly. (‘Energy density’ measures the amount of energy (in kcal or kJ) per weight (usually 100 g) of food. Food supplies that are mainly made up of processed foods, which often contain substantial amounts of fat or sugar, tend to be more energy-dense than food supplies that include substantial amounts of fresh foods.)
  • Avoid sugary drinks
  • Consume ‘fast foods’ sparingly, if at all
  • Eat at least five portions/servings (at least 400 g or 14 oz) of a variety of non-starchy vegetables and of fruits every day
  • Eat relatively unprocessed cereals (grains)
  • Limit refined starchy foods
  • People who consume starchy roots or tubers as staples also to ensure intake of sufficient non-starchy vegetables, fruits, and pulses (legumes)
  • People who eat red meat to consume less than 500 g (18 oz) a week, very little if any to be processed
  • If alcoholic drinks are consumed, limit consumption to no more than two drinks a day for men and one drink a day for women
  • Avoid salt-preserved, salted, or salty foods; preserve foods without using salt; limit consumption of processed foods with added salt to ensure an intake of less than 6 g (2.4 g sodium) a day
  • Aim to breastfeed infants exclusively up to six months and continue with complementary feeding thereafter
  • All cancer survivors should receive nutritional care from an appropriately trained professional
  • If able to do so, and unless otherwise advised, cancer survivors should aim to follow the recommendations for diet, healthy weight, and physical activity

The AICR Newsletter concludes with this advice: “Stay Slim.” Avoid  excessive weight gain. Slim down if you need to. Your  health can benefit in many ways, including lowering your risk for cancer.

Comments are closed.